MOSCOW — Russian and Syrian forces will halt their offensive in the eastern districts of the Syrian city of Aleppo for eight hours on Thursday to allow civilians and rebels to leave the embattled city, the Russian Defense Ministry announced on Monday.

Speaking at a briefing in Moscow, Lt. Gen. Sergei F. Rudskoi, a senior Russian military official, said that Russian and Syrian forces would halt fighting from 8 a.m. to 4 p.m. on Oct. 20. Such “humanitarian pauses” will be regular, he said, and will give temporary relief to the divided city.

Russian and Syrian forces have been bombarding rebel-controlled areas of Aleppo since an internationally brokered cease-fire collapsed last month. Roughly 275,000 people have been subjected to indiscriminate aerial bombing that has killed hundreds.

Russia stopped short of initiating a full-fledged cease-fire, a step that Western governments have been demanding.

“In the current circumstances a unilateral cease-fire would be meaningless,” General Rudskoi told a group of foreign and Russian journalists. “Jabhat al-Nusra and groups allied to it would once again be given time to recover, regroup and restore its military capability,” he said, using the Arabic name for the Nusra Front.

Moscow has been accusing the West of providing jihadist fighters with weapons and other support. General Rudskoi said Russia was working with the United Nations and countries that have influence on the Nusra Front, an affiliate of Al Qaeda that is also known as the Levant Conquest Front, to persuade its militants to leave the city, but that will take time.

He said that Russia was also ready to pause attacks so that humanitarian organizations can evacuate the sick and wounded.

The British ambassador to the United Nations, Matthew Rycroft, on his way to a closed-door United Nations Security Council meeting on Syria on Monday afternoon, said the Russian proposal for a halt in hostilities was one of several proposals to stop the bloodshed.

“What matters is that they stop the bombing of Aleppo and if they’re prepared to do that, anything is possible and until they are, then nothing is possible,” Mr. Rycroft said.

“There are all sorts of steps that can be taken to increase the pressure on them and that’s what we’ve been discussing with our partners in London yesterday, and what we will be talking again and again here this week,” he said, referring to prospective action in the Security Council as well as possible heightened sanctions on Russia.

A United Nations spokesman said on Monday that a pause in fighting in Aleppo would be welcomed, but agencies would require more than eight hours to get aid into the city.

“We will use whatever pause we have to do whatever we can,” the spokesman, Stephane Dujarric, said. “Obviously there is a need for a longer pause in order to get trucks in.”

The United Nations has long called for a minimum cease-fire of 48 hours to organize the delivery of humanitarian aid.

Late on Monday afternoon, Russia’s envoy to the United Nations, Vitaly I. Churkin, said Russia’s offer was “unilateral” and that a longer cessation of hostilities — even one for 48 hours — was only possible when Russia’s principal demand is met: the separation of the Nusra fighters from the other rebel groups.

Pavel E. Fengelhauer, an independent military analyst, said it was possible that Russia wanted to trick the jihadist fighters and lead them into a minefield, a tactic used by its military during a brutal war in the country’s restive republic of Chechnya in 2000 and more recently during the conflict in eastern Ukraine.

“Russia wants Sunni civilians and all rebels to leave the city,” said Mr. Fengelhauer. “This tactic is called military deception.”

Russia first opened escape routes for rebels and civilians out of Aleppo in July, but rights groups said that Syrian government forces had prevented them from leaving. Russia said that rebels shoot at civilians who try to leave.